Model range with index 9 in the nomenclature of BMW, whether it is BMW 9 Series or conceptual development, almost always involves the use of a four-wheel drive system xDrive As the only or the only available solution. This applies to both classic business-class sedans and hypothetical or future crossovers that could receive this index. Engineers of the Bavarian concern historically equip top models with large all-wheel drive indices to ensure maximum course stability and the implementation of high torque of powerful V8 and V12 engines.
BMW car owners often wonder about the distribution of traction when it comes to large bodies, which can be designated with the number 9 in various classifications or internal platform codes. When considering current models, such as BMW X7 (sometimes mistakenly called the nine because of the dimensions) or future flagship coupes, the scheme dominates. AWD. Rear-wheel drive versions (RWD) for such large and heavy cars in modern conditions are extremely rare, usually only in the form of special racing modifications or very old archival models of the early 90s.
Understanding the type of drive is critical for proper transmission maintenance, winter tire selection and diagnostics. An error in determining which drive your car has on its 9 or similar class can result in the wrong crash-down setting or the purchase of inappropriate tires. In this article, we will discuss in detail the technical features of the transmissions used in large BMW models and explain why all-wheel drive has become the standard for this segment.
Historical background and evolution of the index 9
Historically, BMW has rarely used the number 9 to refer to production models in the main sedans lineup, preferring even numbers for coupes and odd numbers for sedans, but settling on the seven as the flagship. However, when it comes to concepts or specific bodywork, the index 9 pops up as a sign of something extraordinary. In the past, there have been projects. BMW 9 SeriesThe sedans were positioned as ultra-luxury sedans designed to compete with the Maybach. In such projects, engineers almost always chose an all-wheel drive scheme for safety and comfort.
In the 90s, when all-wheel drive technology was just being introduced massively, BMW experimented with various schemes. For heavy bodies that could get an index of 9, rear-wheel drive (RWD) was a classic, but it stopped coping with the growing power of the engines. Transition to xDrive It became a necessity. This allowed to transfer torque not only to the rear axle, but also to redistribute it to the front when slipping, which is especially important for heavy cars with a long base.
The modern interpretation of the “nine” is often associated with crossovers or elongated versions of sedans. In these segments, it is the all-wheel drive that dominates. Rear-wheel drive modifications of large crossovers (if they were produced under the index 9) would be ineffective in terms of acceleration dynamics and safety on a slippery road. So, when we answer the question “what drive does 9 have”, we are confident about the dominance of AWD systems in this class.
- 🚗 Classical diagram: For older models, rear-wheel drive is characteristic, but for the class “9” this is rather an exception.
- ❄️ Modern standard: The xDrive all-wheel drive is the main one for all major BMW models of recent years.
- ⚙️ Technological: Index 9 implies the presence of advanced stabilization and traction systems.
Technical features of the xDrive system
System system xDriveThe , which is installed on the model corresponding to class 9, is an intelligent all-wheel drive system. It is based on a multi-disc clutch controlled by electronics. It is able to instantly redistribute torque between the front and rear axles. In standard conditions, the movement often has a rear-wheel drive character, which retains the proprietary controllability of BMW, but at the slightest hint of slipping up to 100% of the moment can go to the front.
An important element of the transmission is the presence of transfer-box (transfer case) Unlike simple plug-in drives, the system works constantly here. Electronics reads data from ABS sensors, throttle position and steering angle. This prevents the sliding before the driver feels it. For heavy bodies, this is critical, since the mass inertia is high, and it can be difficult to correct the demolition of the rear axle at speed.
Maintenance of such a system requires attention. The oil in the transfer box and gearboxes must be changed regularly, despite the manufacturer's claims of "filled for the entire life". For machines with index 9, which are often operated in heavy conditions or with high loads, the interval of oil change in the transfer case It is better to reduce to 60 thousand kilometers. Ignoring this rule can lead to failure of the clutch and expensive repairs.
☑️ Diagnostics xDrive
Differences between RWD and AWD in large bodies
When we talk about big cars, the difference between rear-wheel drive (see below).RWDand complete ()AWD) becomes particularly noticeable. The rear-wheel drive provides cleaner handling in dry conditions and makes it easier to go into a controlled skid, which is appreciated by enthusiasts. However, for everyday use of a heavy sedan or crossover, which could be called a "nine," RWD may be less predictable in rain or snowfall.
All-wheel drive provides the best start from the spot. The thrust is distributed over four wheels, which reduces the likelihood of slipping. For cars with powerful V8 engines, which are often put on top models, this is the only way to realize power efficiently. Acceleration becomes more confident, and the trajectory of movement is more stable. However, it is worth remembering that AWD increases fuel consumption and weight of the car.
The table below compares the characteristics of the two drive types in the context of large BMW cars:
| Parameter | Rear-wheel drive (RWD) | All-wheel drive (xDrive) |
|---|---|---|
| Acceleration 0-100 km/h | Slower (risk of slippage) | Faster (maximum clutch) |
| Fuel consumption | Below (less transmission losses) | Higher (up to 1-2 l/100km) |
| Manageability in snow | Low (chains or spikes required) | High (confident movement) |
| Cost of service | Below (simple construction) | Higher. knots and oils |
Effect of weight on the choice of drive
Heavy cars with an index of 9 have a great inertia. All-wheel drive helps to extinguish this inertia when accelerating and braking the engine, making the behavior of the machine more neutral.
Diagnostics of transmission problems
Owners of all-wheel drive cars need to know the main symptoms of malfunctions. One of the first signs of problems with transfer-box Vibration is a vibration that can occur during acceleration or at certain speeds. There may also be a hum or howl, especially if the oil has not changed for a long time. Ignoring these symptoms can cause the gears and chains inside the node to break down.
Another important aspect is the difference in the diameter of the wheels. For xDrive systems, it is critical that all four tires have the same wear and tear. A difference in diameter even 5-7 mm can lead to constant tension in the all-wheel drive system, as the electronics will try to compensate for the difference in the wheel speeds. This causes overheating of the clutch and its premature wear.
A computer scan is often used for diagnosis. Errors may indicate a faulty wheel speed sensor, problems with the clutch actuator, or a low pressure level in the system. Critically important do not ignore the burning transmission icon on the dashboard, as the system can go into emergency mode by turning off all-wheel drive.
⚠️ Attention: Never tow an xDrive all-wheel drive car with only two wheels raised. This is guaranteed to break the transfer case. Just evacuate on the platform!
The effect of the drive on the choice of tires and disks
Choosing a tire for a car with an index 9 and an all-wheel drive system is not just a matter of comfort, but a technical necessity. As mentioned, the tires should be uniform. If you change only two tires, new ones should be put on the rear axle, and old ones, but still suitable, should be rearranged forward, provided that the difference in the tread is minimal. Ideally for xDrive You need to change a set of four tires at the same time.
Dimension of the disks also plays a role. The use of discs of different radius or departure on different axes is unacceptable. This disrupts the stabilization and all-wheel drive system. For large bodies, discs with diameters between 19 and 21 inches are often recommended, but it is important to consider the rubber profile. Too low a profile can damage the discs and suspension elements on bad roads.
Seasonality matters, too. In winter, all-wheel drive helps to move, but does not help to brake. Therefore, having a quality winter tire kit for a heavy BMW is more important than the type of drive itself. Summer tires on all-wheel drive at temperatures below +7 degrees tan, and the car becomes uncontrollable, regardless of the number of driving wheels.
Tip: When buying used xDrive tires, measure the residual tread height on all four wheels. The difference should not exceed 2-3 mm.
FAQ: Frequently Asked Questions
Can I turn off xDrive all-wheel drive on the BMW 9 Series?
It is impossible to completely mechanically disable the drive on one of the axes in motion, the system works constantly. However, in the car settings menu (iDrive) you can activate the mode DSC Off or special transmission modes that shift the thrust balance closer to the rear axle, simulating the behavior of the rear-wheel drive car. There's also a regime. 4x4x4 (on some models), allowing you to distribute the traction equally for off-road.
What is the resource of the all-wheel drive coupling?
With timely oil replacement (every 40-60 thousand). The xDrive clutch can travel 200-250 thousand kilometers without extreme overloads. The main enemy of the coupling is overheating with prolonged slippage and riding on tires with different wear.
Does all-wheel drive actually increase the cost?
Yes, the presence of additional mechanical elements (cardan, front gearbox, clutch) increases the mass and friction losses. On average, fuel consumption of the xDrive version is higher by 0.5-1.5 liters per 100 km compared to the similar rear-wheel drive version, if such exists for this model.
Do I need to warm up all-wheel drive in the winter?
Yes, it's recommended. The oil in the transmission and gearboxes thickens in the cold. The first 5-10 kilometers of the path, it is desirable to avoid sharp accelerations and slips, to give the lubricant warm up and evenly distributed throughout all nodes of the system. xDrive.
⚠️ Attention: Do not try to disassemble the transfer case yourself without special tools and knowledge. It is a complex assembly that requires fine tuning and calibration after assembly.